If we focus on the \(S\) -wave states, the spin-orbit interactions can be neglected. When integrating over the spatial wavefunction, one can get the improved chromomagnetic model. The Hamiltonian of four-quark states in the ICMI model can be expressed as [1]}, [2]}, [3]}:
\(H=\sum \limits _{i=1}^4m_i+H_{\text{cm}} + H_{\text{ce}},\) 
